title: Lignin content versus syringyl to guaiacyl ratio amongst poplars.
abstract: Two oxidation techniques that afford high yields of monomers and dimers were used to more accurately estimate the syringyl to guaiacyl (S:G) ratio of hardwood lignins. Permanganate oxidation of the woodmeal after a CuO pre-hydrolysis step gave poor results and this was attributed to preferential oxidation and degradation of syringyl nuclei by CuO. However, this procedure did provide a good estimate of the percentages of both S and G phenylpropane (C(9)) units that were uncondensed. When the total S and G products from nitrobenzene oxidation (NBO) of the uncondensed fractions were corrected, credible S:G ratios were obtained. These ratios were in good agreement with results from KMnO4 oxidation of dissolved kraft lignin without CuO pre-hydrolysis. The corrected NBO method was used to determine the S:G ratio of 13 poplars, and the values ranged from 1.01 to 1.68. Unlike results from other investigations, an excellent linear correlation (R(2) =0.846) was obtained for a decreasing lignin content (28% to 16.5%) with an increase in the S:G ratio.
authors.affiliation: Faculty of Paper and Bioprocess Engineering (PBE) and the Empire State Paper Research Institute (ESPRI), SUNY College of Environmental Science and Forestry (ESF), 1 Forestry Drive, Syracuse, NY 13210, USA.
authors.forename: Samar K
authors.initials: SK
authors.lastname: Bose
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Francis
authors.forename: Mark
authors.initials: M
authors.lastname: Govender
authors.forename: Tamara
authors.initials: T
authors.lastname: Bush
authors.forename: Andrew
authors.initials: A
authors.lastname: Spark
mesh_terms: D003300:Copper / Q000737:chemistry; D006868:Hydrolysis; D008031:Lignin / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry; D009578:Nitrobenzenes / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D032107:Populus / Q000737:chemistry*; D014934:Wood / Q000737:chemistry
chemical_list: D017895:Manganese Compounds; D009578:Nitrobenzenes; D010087:Oxides; C048856:permanganic acid; D003300:Copper; C076151:Kraft lignin; D008031:Lignin; C030973:cupric oxide